Copper oxide nanoparticles (CuO NPs) were synthesized in air by reducing copper (II) sulfate pentahydrate salt (CuSO4·5H2O) in the presence of sodium borohydride. The reaction was stabilized with Hexadecyltrimethylammonium bromide (CTAB) in a basic medium and using ultrasound waves. Different molar ratios of CTAB:Cu2+ and NaBH4:Cu2+ were explored, to optimize the synthesis conditions, and to study the stability, size, and Zeta potential of the colloidal suspension. Optimum conditions to generate spherical, stable, and monodispersed nanoparticles with hydrodynamic diameters of 36 ± 1.3 nm were obtained, using 16 mM CTAB and 2 M NaBH4 (molar ratios Cu2+:CTAB:NaBH4 of 1:6:10). X-ray diffraction (XRD) was implemented, and a monoclinic CuO crystal system was formed. This demonstrated a monoclinic crystal system corresponding to CuO. The diffraction peaks were identified and confirmed according to their selected area electron diffraction (SAED) patterns.
The incorporation and effective anchorage of gold nanorods in a gold (111) is applied to electrochemical detection of dopamine. Gold nanorods (AuNRs) were synthesized in dispersion and incorporated in a metal substrate mediated by self-assembled monolayers (SAMs) which act as structural anchors. Two molecular anchors, 4-mercaptobenzoic acid (4-MBA) and 4 aminothiophenol (4-ATP), are compared by charge density (Q) in desorption of the SAMs, where 4-MBA presented a greater coverage on the metal surface. Both SAMs allowed the effective confinement and communication of nanostructure to a greater or lesser extent. Characterizations were made to confirm the constructed system. First, the nanostructures synthesized in dispersion were characterized by UV-visible, transmission electron microscopy, and atomic force microscopy. Then, an electrochemical characterization of the working electrodes include impedance was made. The results focus on the molecular anchor on the activity of electrochemical sensor. Reducing the charge transfer resistance (by at least 90%) of molecularly anchored gold nanorods increases the sensitivity of the electrochemical sensor (at least 20%), the detection of dopamine was studied through a calibration curve, where better sensitivity and detection limit was obtained with the Au/4-MBA/AuNRs system compared to Au/4-ATP/AuNRs.
This research reports the synthesis of copper oxide nanoparticles (CuONP) functionalized by the polar monomers acrylonitrile (ACN) and methyl methacrylate (MMA). The synthesis was achieved by a practical exchange ligand reaction from CuONP previously stabilized by hexadecyltrimethylammonium bromide (CTAB). The replacement of CTAB by ACN or MMA produced the functionalized nanoparticles CuONP-ACN and CuONP-MMA, respectively. The functionalized nanoparticles were characterized by ultraviolet-visible spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (SEM), dynamic light scattering (DLS), Zeta potential, x-ray diffraction (XRD), high-resolution-transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED) analysis. Changes in surface plasmon resonance (SPR) band and the functional group bands observed in UV–vis and FTIR spectra confirmed the efficient replacement of CTAB by polar monomers. Moreover, CuONP-ACN and CuONP-MMA showed a negative surface charge with spherical morphology. X-ray diffraction (XRD) analysis showed that a monoclinic CuO crystal system was formed.
We report on the electrochemical behavior of Ru/C electrocatalysts for the Oxygen Reduction Reaction (ORR) in an acid medium without and with ethanol. As a reference, a Pt/C electrocatalysts was also studied. The results show that Ru/C has a lower catalytic activity for the ORR related to Pt/C in a substance-free electrolyte. However, this study shows that Ru/C possess a high degree of tolerance to C2H5OH, i.e., the shift in onset potential for the ORR () is negligible on this electrocatalyst. In contrast, the catalytic capacity of Pt/C is considerably diminished when alcohol is added to the electrolyte. The shift in from its value in the absence to its value in the presence of C2H5OH on a 10% Ru/C electrocatalyst is 15 times smaller than the shift on 20% Pt/C. Based on these results, the specific application of Ru/C-based electrocatalysts may be in Direct Alcohol Fuel Cells.
Metallo phthalocyanines confined on electrode surfaces such as graphite and carbon materials have been used extensively as active molecular catalysts for a variety of reactions1. When anchored on carbon nanotubes the activity of these catalysts increases by almost 2 orders of magnitude in part due to an increase in effective area. Recently, Cao et al. have shown that anchoring FePc to carbon nanutubes using an axial ligand produces very active materiales for the reduction of O2 in alkaline media, mimicking in this fashion the function of cytochrome c in the catalytic reduction of O2 in living systems. In this work we have used iron phthalocyanines (FePcs) for O2 reduction in basic medium incorporated single wall carbon nanotubes (SWCNTs) modified with pyridiniums axial ligands (py) obtained by reacting diazonium salts. The two phthalocyanines used correspond to the unsubstituted iron phthalocyanine FePc and perchlorinated iron phthalocyanine (16(Cl)FePc)).
Our results show that for ORR:
(i) As expected, carbon nanotubes produce a pronounced increase in electrode surface area, favoring the incorporation of more active sites of the molecular catalysts studied.
(ii) The incorporation of the axial ligand causes an increase in the rate of ORR, resulting in the onset for ORR to more positive values compared to the response of electrodes having FePcs without the axial ligand..
(iii) Of the studied phthalocyanines, 16(Cl)FePc exhibits the highest catalytic activity (Fig.1) due to the synergistic effect of Cl electron withdrawing substituents and the electron withdrawing pyridinium axial ligand.
Acknowledgment:
Fondecyt Nº
1140192 and postdoctoral proyect Nº 3150271.
1. Zagal, J. H., Griveau, S., Silva, J. F., Nyokong, T. & Bedioui, F. Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions. Coord. Chem. Rev.
254,2755–2791 (2010).
2. Cao, R. et al. Promotion of oxygen reduction by a bio-inspired tethered iron phthalocyanine carbon nanotube-based catalyst. Nat. Commun.
4, 2076 (2013).
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